Features of rafters
Rafters - this is the skeleton and the base of the roof. They are necessary to distribute the weight of the roof to the internal supports and walls of the building. Over the rafters lay the crate. Their design directly depends on how the internal supports and attic floors are located, as well as the shape of the roof and the size of the span.
Rafters can be of different shapes - inclined, sliding or hanging. For example, sliding rafters of a saddle roof are used to compensate for the shrinkage of the log. One-pitched roof is considered simple in form and type of structure. The walls can be of different heights, and the inclined part of the saddle roof rests on the walls.
Undoubtedly, the advantage of a saddle roof is the simplicity of its construction, since less force and material is expended. Usually this type of roof is used in non-residential buildings. For the installation of a roof with one slope does not require special skills or knowledge, in addition, this kind of roof allows maximum use of space in the attic.
If a single-sloped roof will crown the residential structure, which also happens, then a good ventilation system must be set up. Normally, special holes for ventilation are drilled, such a roof will be well ventilated regardless of weather or wind direction.
But there is also a minus in the construction of a saddle roof - frequent snow removal, but despite this, this type of roof is often used, for example, in the construction of summer cottages.
Installation and calculation of rafters of a saddle roof
Calculation of rafters of a saddle roof is carried out on two limiting conditions. Firstly, this is a condition for bending strength, and secondly, it is a permissible deflection. You need to determine the cross-section and the number of rafters. If at least one of the two parameters does not correspond to the norm, then the cross-section or the number of rafters increases.
The fastening of the rafters of a saddle roof is as follows: the bar is taken, with a section determined in advance, to fix it better with an "edge" in order to increase the resistance to the deflection to the maximum.
There are several different approaches for fixing the rafters. In the case where the rafters do not lean to the side, but lie on the end of the walls, the fastening of the rafters of the saddle roof occurs directly to the walls with the help of screws with plugs or anchor bolts, it is necessary at least twice to wall the wall. It is desirable that there is a strapping reinforced concrete belt, for the best attachment.
If fixing the rafters to a pre-installed bar, this will take less effort than the previous version, because the holes in the wall will be much smaller. The bar is fixed, and then the rafters are fastened to it with self-tapping screws, often in this case a slot is made in the form of a bar, in order to be "dressed" on it - for greater strength.
When fixing with angles, first the bar is installed, and the rafters are placed on top and fixed by angles and screws at the sides. Remains the roofing over the crate.
Features of metal rafters
Single-skinned roofs made of metal( with steel rafters ) suggest a slightly different mounting process. The profile is also precisely installed to ensure maximum bending strength, for which the edge of the larger side is perpendicular to the roof plane. With this technology, you can consolidate it using several approaches.
The first way - all the rafters are attached to the wall on 's own mounts by drilling a hole in the profile. Next, an opening is made at the end of the wall, a plug is inserted there, then the self-tapping or anchoring bolt of the rafters is tightened to the end. Very good, if there is a reinforced concrete harness belt.
Another type of attachment is welding .For the construction and construction of reinforced concrete strapping, care must be taken to locate the embedded parts, which are plates with anchors that are inserted into the body of the belt, the step of the rafters determines the pitch of the mortgages. After that, the profile is welded to the mortar, and you should not forget about the minimum value of the weld, which is determined depending on the size of the profile and the requirements for the strength of the weld.
